1. Field of the Invention
The present invention relates to a signal transmission circuit and a switch driving device using the same.
2. Description of the Related Art
Conventionally, a signal transmission circuit for transmitting a signal to a back-end side circuit is used in various devices. As an example of the signal transmission circuit, a signal transmission circuit disposed with a level shifting circuit shown in FIG. 15 can be provided.
The signal transmission circuit shown in FIG. 15 is briefly illustrated below. The signal transmission circuit performs level shifting on a pulse signal output from a pulse generator 85 by use of a level shifting circuit 84, and transmits the pulse signal to an RS flip-flop circuit 82.
More specifically, the pulse generator 85 outputs an on signal SON and an off signal SOFF used as pulse signals to a transistor 181 and a transistor 182 respectively. Furthermore, these pulse signals are generated in such a manner that pulses are superposed non-periodically. Moreover, the level shifting circuit 84 is disposed between a power source side (voltage VB) and a ground terminal GND and comprises a series circuit having the transistor 181 and a resistor 183, and a series circuit having the transistor 182 and a resistor 184, and the series circuits are connected in parallel.
In the level shifting circuit 84, the current flowing into the resistor 183 is changed corresponding to the on and the off of the transistor 181, and the current flowing into the resistor 184 is changed corresponding to the on and the off of the transistor 182. The level shifting circuit 84 uses the voltage between the resistor 183 and the transistor 181 as an on signal SON, performs level shifting on the on signal SON to generate a set signal SSET, and outputs the set signal SSET to a reset terminal of the RS flip-flop circuit 82. Moreover, the level shifting circuit 84 uses the voltage between the resistor 184 and the transistor 182 as an off signal SOFF, performs level shifting on the off signal SOFF to generate a reset signal SRESET, and outputs the reset signal SRESET to the reset terminal of the RS flip-flop circuit 82.
Furthermore, the RS flip-flop circuit 82 generates an output signal corresponding to the set signal SSET and the reset signal SRESET, and then outputs the output signal to the back-end circuit. The output signal is used for controlling operation of the device.